Electrical condenser



Patented Oct. i 23, 1928.

UNITED STATES y 1,888,418 PATENT OFFICE.

ARTHUR J. WEISS; F WEST 0RANGE,'NEW JERSEY, ASSIGNOR TO DUBILIER- CON- DENSEB CORPORATION, AOF NEW YORK, N. Y., A CORPORATION OF DELAWARE.

ELECTRICAL CODENSEB.

` l Application led January 13,1927. Serial No. 160,887.

This invention relates to improvements in electrical condensers especially electrical condensers of unchangeable capacity and includlng paper or other fibrous or porous insulation I which is to be impregnated with wax or .some

other suitable liquid dielectric which solidies after the impregnation becomes complete. An object of this invention is to provide a novel condenser and method of impregnating same, of such a character that the insulation will be very eifectual and the condenser much more durable than prior condensers of the class designated; and therefore capable of longer and more satisfactory operation.

Further objects and advantages oi' this'invention are set forth hereinafter; and I reserve the` right to make alterations in structure and the manner of proceeding, without departing from the principle of the invention or exceeding the scope of the appended claims.

On the drawings:

The figure shows in outline a condenser according to my invention and illustrates the method of producing same. l

In the particular description of the drawing, the numeral l indicates the body of the condenser made by winding upv two or more sheets or strips of conductive material, such as metal foil, separated by strips or sheets oi' n paper or other insulation. The roll thus made is compressed into a form of a prism, as shown in the drawing, and is provided with terminals, so that the sheets of metal foil of opposite polarity in the condenser can be connected to an'outside circuit. This type of condenser is 'well-known, and the sheets of metal foil are well-incorporated in the body of the condenser 1, and well covered by 4o the sheets of insulation, and for that reason the sheets of metal foil do not appear on the figure above-mentioned, and only Vconcentric layers of the wound up sheets of insulation are illustrated, and are indicated by the numeral 2. Whensuch condensers arevcompressed into final form, they are usually inipregnated byimmersing in melted paraffin,

or other liquid insulation, to fill the spaces between the layers of insulation and the pores thereof, and prevent the occurrence of small cracks or voids which will give admission to air and moisture. Such voids enable the condenser to become imperfect, and greatly reduce its eiliciencv. The body 1 may be subjected to pressure while the process of impregnation .is taking place, and after cooling, the wax or other liquid insulation solidities and tends to close any minute spaces in the insulation or between ladjacent layers of insulation or metal foil, and sealing the interior of the body of the condenser 1 entirely.

However, during cooling, the liquid insulation with which impregnation is eected, especially if wax is employed, undergoes shrinkage and contraction. while the body of thel condenser may be com- As a result,

pletely impregnated, there will be spaces near the ends shown at the top and bottom oi the ligure, where voids will occur, `particularly near the ends between the edges of'adjacent layers, and at the corners. If the diagonal shade lines. indicated by the numeral 3 represent the distribution of the wax throughout the body of the condenser, the portions at the corners and edges 'adjacent the ends, where no wax or relatively little wax Will remain after impregnation and -when cooling has taken place, is clearly in dicated in the figure, because these diagonal shade lines do not extend all the way to the ends and corners. Therefore, such a condenser may after a while admit air yand 'moisture to the interior through voids occur` ring at the-ends, where the paraffin or other liquid insulation, upon solidifying, has not been retained. The temperature at which the body of the condenser l is impregnated with the liquid insulation may be taken, for example at 285 F. y

To insure full impregnation throughout the body of the condenser all through the places from which the wax might shrink and eventually permit voids to occur, I prefer to put the condenser l through a second process of impregnation after the impregnation with wax has been completed. To this end, the condenser after being removed from the tank containing the melted wax, is laced, While still hot, in a tank containing co d petrolatum, or the like, the tank being pumped for about half an hour to remove air. The

vbody 1 is completely covered Aby the petrola tum and later lair under atmospheric pressure is admitted to the tank. The heat in the body l melts the petrolatum with which it comes into contact, and the petrolatum will soak into the body lat the ends and corners, as indicated at the vertical shade lines 4, and

any voids at the ends and corners will thus be filled by the liquid petrolatum. The condensers remain in the petrolatum until they become cool, and as the paraffin shrinks and contracts up to the point where it solidifies, for example at 130 F., or thereabout, it is followed up by the still yliquid petrolatum which penetrates in through the ends as far as the wax 3 shrinks. Thus, -all voids are filled up, and as the cooling continues until it approaches room temperature, the petrolatum also becomes thicker and\more nearly solid, and will not run ,out of the body of the condenser,`but stick inside of the ends and corners thereof, and thus complete the efl'ect which the impregnation with paraffin does not fully insure.

It is to be understood that by impregnation of a condenser I refer to the displacement'of all air and moisture, or the complete filling of voids and interstices, for all practical purposes, within the condenser body as distinguished from any proc css in which the condenser is merely dipped or coated. Altho the dipping or coating compound may penetrate into the condenser body, the latter process does not insure the displacement of all air and moisture, or prevent the formation of voids therein.

Condensers worked as above will safely withstand far higher voltages than condensers impregnated in the usual way, with paraiiin, wax, or some other liquid compound of that nature.

When paper condensers are treated to impregnate them with wax they must always be heated to eliminate moisture and air andmake the wax fluid'enough to penetrate the condensers. All waxes have a large coefficient of expansion; and whenever a condenser im-' pregnated with wax cools, the wax contracts to a large extent; and the contraction is what causes spaces and voids in the condenser. As described above the voids and spaces are apt to occur particularly at the ends. Also, the wax in hardening and contracting exerts mechanical forces and stresses on the paper which ma do injury, besides giving rise to voids an cracks, and the condenser will break down in time. But if the condenser, while still warm, after being impregnated with wax is placed into petrolatum, or similar insulating substance, the petrolatum will prevent the condenser from becoming as hard as when wax is used alone and will fill in voids and prevent such spaces and voids from forming. No' mechanical strains will then occur and the condenser will'be much more durable and withstand higher voltages in service.

As stated above, the effect of plunging the 'body of a condenser while still hot into petrocorners and all other parts which are left empty by the wax. Ihave stated that petrolatum or the like may be employed and I havefound that heavy oil answers very Well, particularly an 'oil of such a nature which willliave characteristics similar to-those of ypetrolatum when petrolatum is melted.

It has long been |known in the art that a condenser which will satisfactorily withstand a potential several times greater than ally increases in service and eventually causes` a break-down of the dielectric, but in the process disclosed ionization is prevented by the fact that no voids are formed by the shrinkage of thc impregnating compound, due to the use of a second compoundwhich follows up and fills all ofthe interstices as the first impregnating compound cools.

Having described my invention, what I believe to be new and desire to secure and protect by Letters Patent of the United States is -1. The method of treating a condenser body which comprises impregnating the same in a heated insulating compound, immersing the bodywhile heated in another compound having a lower melting point, and cooling the body while so immersed.

2. The method of treating a condenser body which comprises impregnating the same in heated Wax, iminersing the body while heated in cooling oil," and permitting the body to cool while so immersed.

3. The process of treating a condenser body which consists in impregnating the same in a heated insulating compound which contracts upon cooling, removing the body from the compound and immersing the same while hot in a cooling compound having a'lower melting. point, and permitting the body to cool while so immersed whereby the lastnamed compound will follow up the firstnamed compound as it contracts and thereby Ervent the formation of voids within the 4.. The process of impregnating a condenser containing insulation which consists in first immersin it in ia' heated insulating material which ge temperatures and shrinks upon cooling to pervade the greater part of the body of the condenser, treating the body before said insulating material has cooled with another compound, and cooling the body while so treated to impregnate the remaining portions thereof.

'5. The process of 'treating a condenser comes solid at ordinary immersing the same 'while' hot in petrolatum,

exhausting air and subsequently admitting air and cooling the-body while so immersed so that as the wax which impregnates the greater portion-ofthe body shrinks and contracts upon cooling, the remaining outer portions of the body will be filled with petrolatum and the body thus fully impregnated throughout.

Y; A condenser body impregnated with an 'insulating compound throughout the greater portion thereof, and impregnated further with another compound throughout its remaining portions, said body being free from voids and having all interstices filled with -compound.

8. A condenser including a body containing porous insulation and impregnated with4 wax throughout the greater portion of thebody thereof, and impregnated further with petrolatum throughout the remaining porl tions of the body, said body being free from voids and having all interstices illed with' impregnating com ound.

9. A condenser od including armatures separated by body being lmpregnated throughout its central portion with a compound having a given meltmgpoint and which contracts upon cooling, sai body being impregnated throughout itsremaining outer portions with a compound havin a lower melting point.

10. A con enser having abody containing porous insulation impregnated with a plurality of insulating compounds having different melting points, each of the compounds occupying different portions of the body, body being free from voids and having all interstices filled with compound.

11. A condenser having a body containing porous insulation impregnated in certain portions lthereof with `an insulating compound which is hardvat ordinary temperatures and impregnated in other portions thereofwith an insulating compound'which is viscous at ordinary temperatures.

12. A condenser body impregnated throughout the greater ortion thereof with an insulating compoun .which is -hard at Ordinar tem eratures, the edges of the condenser ody eing impregnated with an insulating compound which is soft at ordinary temperatures.

In testlmony whereof AI aix my signature. f ARTHUR J. WEISS.

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